Abstract:

Cave dwelling animals are well studied examples of environmental cues leading to regressive evolution. Losing complex traits such as vision is thought to be due to negative selective pressures on light sensitive functions from life in perpetual darkness. Genetic analysis of these genes has provided insight into functionality of lost traits as well as varying selective pressures driving evolution in the dark. To characterize vision loss in cavefish, we analyzed the do-novo transcriptome of Phreatobius cisternum for visual and non-visual opsins and compared the results to a surface relative, Ictalurus punctatus (Channel catfish), as well as Danio rerio (Zebrafish). We’ve identified 11 opsins in the transcriptome compared to 23 of Channel Catfish, with only Rh1 being a complete gene and the others in fragments, as well as retaining introns. We calculated dn/ds values of each opsin and found evidence against neutral molecular evolution and for purifying selection. Preliminary evidence of retaining function in certain cavefish opsins (such as Rh1) suggests opsins may have other roles than light sensing capabilities. Future research includes comparing the genome of Phreatobius to our results to better understand opsin evolution.